
def letters(letter):
    restr=""
    for i in letter:
        if i.isalpha():
            restr = restr + i
        else:
            continue
        return restr

def reverse(str):
    if str=="":
        return str
    else:
        return reverse(str[1:]+str[0])

letter = input("输入字符串:")
print("处理后的字符:{}".format(reverse(letters(letter))))